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Chapter 2&3

Ch.2 & 3-Evolution and Genetics.docx

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Genevieve Dewar

Prashanthan Sep/18/2012 Evolution and Genetics Ch.2  Earliest human ancestors evolved from species that lived ~5-8mya o Did NOT evolve from monkeys/chimps A Brief History of Evolutionary Thought  Fixity of Species: notion that species, once created, can never change  James Ussher: concluded that Earth was created 4004BC  John Ray: developed concept of species (groups of organisms that can breed together) and genus  Carolus Linnaeus: developed binomial nomenclature (genus and species name used to refer to species) and taxonomy (science that classifies organisms) o First to consider humans as animals (by classifying humans as homo sapiens in animal kingdom)  Jean-Baptiste Lamarck: first to explain evolutionary process o Body parts would be modified depending on their use  Inheritance of Acquired Traits / Use-Disuse Theory o Eg. giraffe necks grew longer b/c they were stretched (used more often)  Georges Cuvier: concept of extinction to explain disappearance of animals represented by bones o Catastrophism: Earth’s geological landscape results from violent cataclysmic events  Organisms would die, and be replaced by more “modern” organisms  Thomas Malthus: pop. growth is restricted by food supply  Charles Lyell: Uniformitarianism (Earth’s features result from long-term process that continue to operate as they did in the past)  Charles Darwin: Natural Selection (genetic change of frequencies of certain traits in pop due to reproductive success)  Alfred Russel Wallace: Developed a similar theory to natural selection around the same time that Darwin did Natural Selection  Basic processes that led to Natural Selection 1. All species produce offspring faster than food supplies increase 2. Biological variation exists in all species 3. Since not all produced offspring survive, there is competition b/w individuals for resources 4. Individuals with favourable traits have advantage over those that don’t 5. Environmental context determines whether trait is beneficial or not 6. Traits are inherited and passed to next generation. Beneficial traits are passed on, while non-beneficial traits die off, and aren’t passed onto future generations. 1 Prashanthan Sep/18/2012 7. Over time, new species may appear b/c generations may be distinct from ancestors 8. Geographical isolation contributes to formation of new species, and adapt to those enviros Natural Selection in Action  2 peppered moths (dark and light gray)  Light gray was more prevalent b/c they would camaflouge with tree trunks o Dark gray couldn’t camouflage, and were killed by predators  Industrial revolution lead to coal dust being spread, covering tree trunks o Dark grey camouflaged, while light moths were easily spotted and eaten by predators  Once air was cleaned, trees became normal color, and light moths camouflaged better again  Fundamentals of evolutionary change produced by natural selection o A trait must be inherited(hereditary) if natural selection is to act on it o Natural selection can’t occur without pop variation in inherited characteristics o Fitness is a relative measure of reproductive success that changes as environment changes o Natural selection can act only on traits that affect reproduction (before reproduction) Opposition to Evolution  Quite a few ppl don`t believe in evolution o Complex process that is difficult to explain with simple explanations o Raised in belief systems that don`t emphasize biological continuity (idea that organisms are related thru common ancestry and traits present in 1 species also seen to varying degrees in others) o Religion that supports creationism Ch.3 The Cell  Nucleus: organelle that contains chromosomes (nuclear DNA)  Deoxyribonucleic Acid (DNA): double-stranded molecule that contains genetic code  Ribonucleic Acid (RNA): similar structure to DNA, used for protein synthesis  Cytoplasm: semi-fluid material that contains numerous structures involved in cell function  2 types of cells o Somatic: all cells in body EXCEPT those involved in reproduction o Gametes: reproductive cells (sperm and eggs)  Eggs produced in ovaries, sperm produced in testes  Zygote: cell formed by union of egg and sperm cell, contains full complement of chromosomes and has potential to develop into entire organism DNA Structure and Function  DNA made up of nucleotides (made up of sugar, phosphate and 1 of 4 DNA bases) 2 Prashanthan Sep/18/2012  4 bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C) o A always binds to T o G always binds to C  Enzymes break bonds b/w DNA, separating the 2 strands, and leaving the bases exposed  Exposed bases attract unattached complementary bases (making a new strand)  Parental DNA strands serve as templates for synthesis of new strands  Some proteins capable of attaching to DNA (regulatory proteins) to influence genes  Proteins made up of amino acids o 20 diff types of amino acids exist, and can be combined in many ways to produce millions of diff proteins  Sequence of bases on DNA determine order of amino acids o Group of 3 bases codes for specific amino acid (eg. CGA codes for alanine) o If mutation changes the coding of an amino acid, protein structure might be influenced, and its function will differ  Gene: sequence of DNA bases that specify the order of amino acids for a protein  Segments of DNA that code for amino acidsexons o However most of DNA in gene isn’t expressed during protein synthesis (introns)  Regulatory Gene: genes that code for proteins that influence action of other genes  Homeobox (Hox) Genes: ancient family of regulatory genes that pattern overall body during embryonic development o eg. influence diff types of verterbrae, where limb buds appear in embryo o don’t vary greatly from species to species o changes in behaviour of hox genes influences physical results in physical differences Cell Div
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